Flutter - 如何从父级调用子级小部件的方法

Question

Let's say we have two stateful widgets .

ParentWidget(){

}

ChildWidget() {
  someMethod(){
    // some code, for example setState code
  }

}

Now when I use the ChildWidget in ParentWidget , how do I call the someMethod() ?

Answer 1

If you need call function on widget you can use:

context.findAncestorWidgetOfExactType<T>()

If you need call function on state of that widget you can use:

context.findRootAncestorStateOfType<T>();

read more at:

https://api.flutter.dev/flutter/widgets/BuildContext/findAncestorWidgetOfExactType.html

https://api.flutter.dev/flutter/widgets/BuildContext/findRootAncestorStateOfType.html

Answer 2

Here is way what I've used.

• Make a GlobalKey instance
• Pass the Globalkey as a Key parameter to child widget.
• Call GlobalKey.currentState.method();

GlobalKey<ChildWidgetState> globalKey = GlobalKey();

ParentWidget(){

   ChildWidget(key: globalKey);

   ...

   globalKey.currentState.someMethod();


}

ChildWidget() {
  ChildWidget({Key key}) : super(key: key);

  someMethod(){
    // some code, for example setState code
  }

}

TestCode

import 'package:flutter/material.dart';

const Color darkBlue = Color.fromARGB(255, 18, 32, 47);

void main() {
  runApp(MyApp());
}

GlobalKey<ChildWidgetState> globalKey = GlobalKey();

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData.dark().copyWith(
        scaffoldBackgroundColor: darkBlue,
      ),
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        body: Center(
          child: MyWidget(),
        ),
      ),
    );
  }
}

class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        InkWell(
          onTap: () {
            globalKey.currentState.someMethod();
          },
          child: Text('ParentWidget'),
        ),

        ChildWidget(key: globalKey),
      ],
    );
  }
}


class ChildWidget extends StatefulWidget {
  ChildWidget({Key key}) : super(key: key);
  
  @override
  ChildWidgetState createState() => ChildWidgetState();
  
}

class ChildWidgetState extends State<ChildWidget> {
  void someMethod() {
    print('someMethod is called');
  }
  @override
  Widget build(BuildContext context) {
    return Text('childWidget');
  }
}